A hydraulically assisted power steering gear with a detent mechanism typically has a steering gear input member and a steering gear output member. As vehicle speed increases, the detent mechanism tends to mechanically engage the output member to the input member with increasing force, mechanically positioning the output member with the input member to a mechanically balanced position. The relative orientation between the input member and the output member in the mechanically balanced position is typically determined by plungers or spheroids, rotating with the output member, being pressed into detent recesses in the input member.
A rotary hydraulic valve has a spool portion integral with the input member and a sleeve rotatively fixed to the output member. The hydraulic valve is trying to position the output member relative to the input member simultaneous with the detent mechanism trying to position the output member relative to the input member. If the valve spool portion is not in a hydraulic on center position, that is, not in a hydraulically balanced position, with respect to a valve sleeve, the valve supplies fluid to a bi-directional actuator which causes the output member, and hence the valve sleeve, to rotate back toward the hydraulically balanced position.
Because both the valve spool portion and the recesses in the input member are integral with the input member, the hydraulically balanced position cannot be selectively aligned with the mechanically balanced position by rotating the valve spool portion relative to the recesses.